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. 2016 Dec 1:6:38007.
doi: 10.1038/srep38007.

Surface Protonics Promotes Catalysis

R Manabe  1 , S Okada  1 , R Inagaki  1 , K Oshima  2 , S Ogo  1 , Y Sekine  1
Affiliations

Surface Protonics Promotes Catalysis

R Manabe et al. Sci Rep. .

Abstract

Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando-IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd-CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

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Figures

Figure 1
Figure 1. Temperature dependencies of catalytic activity with or without electric field.
(A) Activities for steam reforming (SR) and Electreforming (ER), (B) Arrhenius plots for both reactions, preset temperature, 398–823 K; catalyst, 1.0 wt% Pd/CeO2, 80 mg; flow, CH4: H2O: Ar:He = 12: 24: 12: 72, total flow rate 120 SCCM; current, 0 or 5 mA.
Figure 2
Figure 2. Operando-DRIFTS spectra with/without electric field.
(A) Comparison for with/without Pd or application of electric field, (B) O-H rotating region, (C) O-H stretching region, catalyst, CeO2 or 1.0 wt% Pd/CeO2; flow, CH4: H2O: Ar = 1: 2: 62, total flow rate 65 SCCM; current, 0 or 5 mA.
Figure 3
Figure 3. IR band intensities of CH4 gas (3016.6 cm−1) at 473 K in electric field.
(A) With/without H2O, (B) with H2O/D2O, catalyst, 1.0 wt% Pd/CeO2; flow, CH4: H2O/D2O: Ar = 1: 2(0): 62(64), total 65 SCCM; current, 5 mA.
Figure 4
Figure 4. Pd specific surface area (TOF-s) dependency or Pd perimeter (TOF-p) dependency of activities for ER at 473 K and SR at 673 K.
(A) ER at 473 K, (B) SR at 673 K, catalyst, 1.0 wt% Pd/CeO2; flow, CH4: H2O: Ar = 1: 2: 62, total 65 SCCM; current, 0 or 5 mA.
Figure 5
Figure 5. Schematic image of reaction mechanism for Electreforming.
See this image and copyright information in PMC

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